1. Field of the Invention
The present invention relates to a viscous rotary damper that is applied to a hinge of an automotive closure system such as tailgates, doors, trunks, liftgates, decklids, etc.
2. Description of Related Art
Current entry/exit door systems in an automobile often use mechanical devices to provide soft stop locations or checks between a fully open position and a fully closed position, and a hard stop at the fully open position. However, the operation of these mechanical devices may be perceived to be “harsh” by the end user. It is especially difficult to control the door bounce back from the fully open hard stop location by using these mechanical devices. When the end user opens the door and moves the door into the fully open position, the system does not readily absorb the energy of the door moving in the opening direction, and thus the door may tend aggressively to bounce back onto the end user.
Current hood, trunk, liftgate and tailgate systems in an automobile typically use strut systems to provide open assist and velocity control. However, these strut systems are more expensive (typically requiring two struts per hood, trunk, liftgate or tailgate). See, e.g., U.S. Pat. No. 6,994,390. These strut systems are large, require more packaging space within the vehicle and can potentially cause pinch points to the end user. These strut systems may also be subject to significant performance changes due to changes in the temperature. For example, these strut systems provide low or inadequate assist at low temperatures and provide high or excessive assist at higher temperatures. These strut systems also require additional structural support mechanisms (such as body reinforcements) and supplemental attaching features (such as ball studs).
Viscous dampers are used in the automotive industry, for example, to provide rotational resistance on a hinge shaft of an opening-closing member, such as a console box or a glove box, so that the opening-closing member is not suddenly closed or opened (e.g., see U.S. Pat. Nos. 5,497,863; 5,887,930; 6,085,384; 6,840,356 B2; and 7,066,308 B2). These viscous dampers are too small for the hinge systems that are used in other automotive closures systems, such as tailgates, doors, trunks, liftgates or decklids, which require resistance torque in the range of 15 to 25 Nm. The viscous dampers that produce the required resistance torque are larger in size and cannot meet the limited space requirements for the hinge systems.
Additional references of interest include U.S. Pat. Nos. 3,952,365; 5,084,939; 5,979,592; and 7,051,618 B2; U.S. Patent Pub. Nos. 2001/0007163 A1 and 2004/0103746 A1; EP 01413794 B1; EP 01650468 A1; EP 00978615 B1; and JP 03139427.